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Abstract
Epiphyas postvittana (Walker) resistant to azinphos-methyl caused 1.7 and 5.4% fruit damage in 1983/84 and 1985/86 in apple orchards at Moutere Bluffs, New Zealand. Surveys from 1984 to 1989 of resistance in orchards and scrub nearby showed 3.5% survival of the diagnostic dose (LD99.95) in January and 7.6% survival in April. Survive did not increase between years. Catches in pheromone traps inside affected orchards indicated high levels of male activity despite regular application of chlorpyrifos. Mating disruption, along with the application of chlorpyrifos, was investigated as a possible solution to the continued inability to achieve economically acceptable leafroller control with insecticides alone. Two ha of apple trees were treated with Shin Etsu Chemical Co. dispensers (1000/ha) containing (E)-11-tetradecenyl acetate and (E,E)-9, 11-tetradecadien-1-yl acetate (56.5 and 2.8 mg per dispenser), in January 1987. No males were caught for over 11 months after the pheromone application. Harvest damage of the apple variety ‘Sturmer Pippin’ by lightbrown apple moth in the 1986/87 season was reduced to 0.02% from 5.4% in 1985/86. In January 1988, dispensers were applied at the same application rate in the same area, and one less chlorpyrifos application was made (total of 10). At harvest, 0.02% fruit damage was again detected. In 1988/89, the area treated with pheromone dispensers was increased to 10.6 ha, and the application made in November 1988. Fruit damage in the block treated for the third year was reduced to 0.0072% despite the elimination of three insecticide applications. Packhouse assessments indicated that fruit from three orchards in the area treated with pheromone and which received 6–7 insecticides averaged the same or less damage compared with fruit on similar blocks after 9–11 insecticide applications without pheromone. Implications for the use of mating disruption with insecticide applications are discussed.